Lallyr, Malpensa is in the middle of nowhere.

IIRC the last bus to the city leaves around 10, maybe even 10.30 p.m and that is your last halfway cheap possibility to get into town late, beside a cab ( Euro 50-70 ) or a rental car ( huge surcharges in Italy )

For more info, please also see:
http://www.sea-aeroportimilano.it/eng/

Did not visit the ( contracted )KL lounge there, was running pretty late, but there was a discussion about it before, maybe a search ( FT archives ? ) would help.